As is generally known, a hybrid electric vehicle uses an internal combustion engine and a battery power source together. That is, the hybrid electric vehicle efficiently combines and uses power from the internal combustion engine and power of a motor.
The hybrid electric vehicle generally includes the engine, the motor, an engine clutch controlling the power between the engine and the motor, a transmission, a differential gear device, a high voltage battery, an integrated starter & generator (ISG) starting the engine or generating power by an output of the engine, and wheels.
Further, the hybrid electric vehicle may include a hybrid control unit (HCU) controlling the entire operation of the hybrid electric vehicle, an engine control unit (ECU) controlling an operation of the engine, a motor control unit (MCU) controlling an operation of the motor, a transmission control unit (TCU) controlling an operation of the transmission, and a battery control unit (BCU) controlling and managing the high voltage battery.
The engine control unit may be called an engine management system (EMS). The battery control unit may be called a battery management system (BMS). The integrated starter & generator may be called a hybrid starter & generator (HSG).
The hybrid electric vehicle may travel in a driving mode, such as an electric vehicle (EV) mode using only the power of the motor. A hybrid electric vehicle (HEV) mode uses rotation force of the engine as the main power and rotation force of the motor as auxiliary power by engaging or releasing the engine clutch according to acceleration and deceleration intention of a driver depending on an operation of an accelerator pedal and a brake pedal, a vehicle speed, and a state of charge of the battery. A regenerative braking mode collects braking and inertial energy through the power generation of the motor during driving by braking or inertia of the vehicle to charge the collected energy in the high voltage battery.
When the hybrid electric vehicle converts the EV mode into the HEV mode, the engine clutch is engaged after an engine speed and a motor speed synchronize with each other, and as a result, a torque change is not generated during a power transferring process between the engine and the motor which are different power sources to secure drivability.
As such, the hybrid electric vehicle uses both mechanical energy of the engine and electrical energy of the high voltage battery, and uses an optimal operation area of the engine and the motor and collects the energy to the motor during braking, and as a result, fuel efficiency may be improved, and energy may be efficiently used.
In order to drive in a fail safe mode of the hybrid electric vehicle, it is required to determine whether the engine follows an engine torque command or the motor follows a motor torque command. To this end, it is required to know a torque and a speed of the engine and a torque and a speed of the motor.
In the hybrid electric vehicle, since controlling the torque acts as an important factor for improving drivability, a research for the torque control has been conducted.
In general, an engine speed sensor measuring the engine speed and a motor speed sensor measuring the motor speed are mounted in the hybrid electric vehicle, but a torque sensor measuring the engine torque and a torque sensor measuring the motor torque are not installed due to a problem such as costs. Accordingly, in the related art, the engine torque is predicted based on air flowing into the engine and a fuel amount, and the motor torque is predicted based on a voltage and a current input to the motor to control the vehicle according to a prediction value, but there is a problem in that reliability deteriorates.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.